For directional drilling, the bottom hole assembly BHA is normally equipped with a measurement while drilling MWD for determining the trajectory and a steerable machine to allow control of the trajectory of the well bore. The steerable machine may be either a steerable motor, which requires a sliding mode to steer the well, or a rotary steerable system RSS. In the low tier market and high dog-leg market, a steerable motor may be the preferred solution because of low system cost, capability of high dog-leg, and limited fatigue on the drill-string as partial sliding in the curve. Steering capability can be useful when drilling a vertical section and avoiding collision. It may also be useful to kick-off from vertical below a casing where measurement while drilling MWD magnetometer be may perturbed by the casing.
U.S. Pat. No. 9,404,307, incorporated herein in its entirety by reference, discloses a known directional drilling system. As shown in FIG. 1, a drilling rig (“rig”) 11 includes a derrick 13 that is supported on the ground above a rig floor 15. The rig 11 includes lifting gear, which includes a crown block 17 mounted to the derrick 13 and a traveling block 19. The crown block 17 and the traveling block 19 are interconnected by a cable 21 that is driven by a draw works 23 to control the upward and downward movement of the traveling block 19. The traveling block 19 carries a hook 25 from which a top drive 27 may be suspended. The top drive 27 rotatably supports a drill pipe string (“drill string”) 35, in a wellbore 33. The top drive 27 can be operated to rotate the drill string 35 in either direction, or to apply a selected amount of torque to the drill string 35. The drill string 35 may be coupled to the top drive 27 through an instrumented top sub 29. A surface drill string torque sensor 53 may be provided in the instrumented top sub 29. A surface drill pipe rotational orientation sensor 65 that provides measurements of drill string angular position or “surface” tool face may also be provided in the instrumented top sub 29. The instrumented top sub 29 may be a device sold by 3PS, Inc., Cedar Park, Tex. known as an “Enhanced Torque and Tension Sub.”
The surface drill string torque sensor 53 may be implemented as a strain gage in the instrumented top sub 29, or as a current measurement device for an electric rotary table or top drive motor, or as a pressure sensor for a hydraulically operated top drive. The surface drill string torque sensor 53 provides a signal which may be sampled electronically. The orientation sensor 65 may be implemented as an integrating angular accelerometer (and the same may be used to provide measurements related to surface torque). Irrespective of the instrumentation used, the surface drill string torque sensor 53 provides a measurement corresponding to the torque applied to the drill string 35 at the surface by the top drive 27 or rotary table (not shown), depending on how the rig 11 is equipped. Other parameters which may be measured, such as fluid pressure in the drill string 35.
The drill string 35 may include a plurality of interconnected sections of drill pipe (tubulars or stands) (not shown separately) and a bottom hole assembly (“BHA”) 37. The bottom hole assembly 37 may include stabilizers, drill collars and a suite of measurement-while-drilling (“MWD”) instruments, including a MWD tool direction sensor 51. The MWD tool direction sensor 51 provides, among other measurements, tool face angle measurements, as well as wellbore geodetic or geomagnetic direction (azimuth) and inclination measurements. A steerable drilling motor (“steerable motor”) 41 may be connected near the bottom of the bottom hole assembly 37. The steerable motor 41 may be a positive displacement motor, a turbine, or an electric motor that can turn the drill bit 40 independently of the rotation of the drill string 35. The tool face angle of the drilling motor may be used to correct or adjust the azimuth and inclination of the wellbore 33 during slide drilling. The rig operator (“driller”) may operate the top drive 27 to change the tool face orientation of the steerable motor 41 by rotating the entire drill string 35. A top drive 27 for rotating the drill string 35 is illustrated in FIG. 1. Other equipment includes a rotary table and kelly bushing (neither shown) to apply torque to the drill string 35.
Drilling fluid is delivered to the interior of the drill string 35 by mud pumps 43 through a mud hose 45. During rotary drilling, the drill string 35 is rotated within the well bore 33 by the top drive 27. The top drive 27 is slidingly mounted in the mast on parallel vertically extending rails (not shown) to resist rotation as torque is applied to the drill string 35. During slide drilling, the drill string 35 may be held rotationally in place by the top drive 27 while the drill bit 40 is rotated by the steerable motor 41. The steerable motor 41 is ultimately supplied with drilling fluid by the mud pumps 43 through the mud hose 45 and through the drill string 35. The cuttings produced as the drill bit 40 drills into the subsurface formations are carried out of the wellbore 33 by the drilling fluid supplied by the mud pumps 43. The discharge side of the mud pumps 43 may include a drill string pressure sensor 63. The drill string pressure sensor 63 may be in the form of a pump pressure transducer coupled to the mud hose 45 running from the mud pumps 43 to the top drive 27. The pressure sensor 63 makes measurements corresponding to the pressure inside the drill string 35. Some implementations of the instrumented top sub 29, for example, may include a pressure sensor.
In view of prior drilling systems, there is a need for drilling system to perform some directional drilling operations with no, or at least minimum, equipment in the well-bore, i.e., no measurement while drilling MWD in the well-bore.